Plan and manage client access

• Namespace planning
• URLs and virtual record configuration
• Management of Exchange certificates widespread
• Troubleshooting of the client’s access connectivity issues
• Configuration of worldwide Outlook on the Web plans
• Auto Discover configuration
• Addition and management of Domain Keys Identified Mail (DKIM) signs to domains

Securing Messaging Environments: 20-25%

• Manage Compliance: this objective covers the individuals’ skills in configuring Office 365 Labels, Exchange data loss inhibition policies, Exchange retention & retention policies, as well as managing content search, eDiscovery cases, and journal rules.
• Manage Role-Based Permissions: this topic requires your skills in managing role groups and the role of users, assigning user accounts to the admin roles, and managing delegated RBAC setups.
• Manage Message Hygiene with Office 365 ATP and Exchange Online: the test takers will be evaluated based on their skills in planning for messaging hygiene, configuring malware and spam filters, managing connection filters and protection for phishing, configuring and managing ATP safe attachments, safe links, anti-phishing, as well as Office 365 anti-spam.

Reference: https://docs.microsoft.com/en-us/learn/certifications/exams/ms-203